The exhaust systems of some vehicles include active exhaust valves (AEVs) configured to modulate the flow of gasses through the exhaust system. The AEVs can be used to control engine performance as well as the acoustic attributes of the vehicle's exhaust. Generally, the positions of each of the AEVs are set based upon control signals transmitted by the vehicle's engine ECU or some other suitably configured controller within the vehicle.
During operation, many AEVs generate diagnostic signals that are transmitted to the ECU to indicate whether the AEVs are operating correctly. The diagnostic signals may indicate an overall health of the AEVs as well as provide information regarding the current position and operating conditions of the AEVs. In some situations, the diagnostic signals may indicate that an AEV has failed. Alternatively, the fact that a particular AEV has failed to transmit a diagnostic message may be used as an indication that the valve has failed. For AEVs that are not configured to transmit diagnostic messages, a failure can be detected by other mechanisms, such as via a feedback position sensor or the AEVs control electronics. Upon detecting that one or more of the AEVs has failed or is otherwise malfunctioning or non-communicative, the ECU can then take appropriate corrective action.
At high engine speeds, it is important that the engine's exhaust system provide high exhaust flow allowing for efficient dispersal of exhaust heat. Accordingly, as engine speed varies, the positioning of the AEVs is adjusted to provide for effective exhaust flow and corresponding cooling. In the event of a failure or malfunction of one or more AEVs, the correct position of the AEVs cannot be determined. Because there is some risk that the AEVs failed in a substantially closed position, which could result in a dangerous build-up of heat within the exhaust systems and engine, the engine speed must be limited to prevent overheating and damage.
Sometimes aftermarket exhausts are installed into vehicles. To save weight, the aftermarket exhaust may not utilize exhaust valves and instead have a substantially high-flow design. Although such an aftermarket exhaust may be an entirely safe addition to the vehicle—their open flow design ensuring sufficient exhaust gas flow—in the case of an aftermarket exhaust that does not use or connect to the vehicle's AEVs, the engine's ECU will not receive any diagnostic signals from the AEVs. This may cause the ECU to believe that the AEVs have failed and reduce engine performance to compensate. This, however, is not necessary as the aftermarket exhaust provides sufficient exhaust flow for safe operation of the vehicle without the need for AEVs. As such, the ECU needlessly reduces engine performance.